Hundreds of protesters demanding an investigation of Mayor Rahm Emanuel's administration flooded downtown Chicago streets Wednesday afternoon as part of a citywide walkout just hours after Emanuel publicly apologized for the shooting death of Laquan McDonald and vowed to fix broken Chicago police practices.

The group chanted "Whose city? Our city," "Who's got to go? Rahm's got to go," and "No more killer cops."

Demonstrators gathered at Daley Plaza at noon and started marching on North Dearborn. Police briefly detained two people during the protest near Dearborn and Washington as several other activists gathered around the vehicle chanting "Hell no, we won't go." The two demonstrators were later released.

"It's bigger than the shooting of Laquan MCDonald, the murder of Percy Coleman's son, it's bigger than Ronnie man, Ronald Johnson," said Willie J.R. Fleming with the Anti-Eviction Campaign. "It's a cultural corruption. It's the daily practice and procedures of the Chicago Police Department, the City Council of Chicago and the mayor's office."

An estimate on the number of demonstrators involved in the march wasn't immediately clear, but more than 1,800 people said in a Facebook group they would attend the walkout.

"We will now hold our leaders accountable for the transgressions they commit and that are committed under their watch," the group wrote on Facebook. "Task forces, press releases, symbolic replacements of one crony for another are no longer enough to mollify the masses."

Earlier, protesters gathered at City Hall, calling for the mayor's resignation.

About 200 protesters gathered outside council chambers during Emanuel's special address to the city council and demanded to be let inside. They said one mayoral speech can't fix decades of police corruption that led to 17-year-old McDonald's death at the hands of officer Jason Van Dyke. At one point, a fight broke out.

"This is going to get a lot bigger than what it was," Jeffrey Coleman told NBC Chicago, pointing to intense anger among Chicago residents and alleged abuse by police officers that he said has led to "disrespect and murder in our community."

"It's disappointing," said Bishop Tavis Grant, a spokesman for the family of 38-year-old Phillip Coleman who died in 2012 while in Chicago police custody. Recently released video of the incident shows a group of officers shooting Coleman with a Taser before dragging his body down a hallway while handcuffed. Coleman died a day later.

"There was not a real apology," Grant said of Emanuel's speech, "and Phillip's name was not mentioned. It's not enough. We're going to see protests lead to unrest unless we see constructive change that leads to justice."

Demanding change and calling for an investigation of the mayor, demonstrators remained inside City Hall well after Emanuel's speech.

On Thursday, a 5 p.m. rally is planned by the Chicago Alliance Against Racist & Political Repression.

The release last month of a video showing the 2014 killing of a black teenager by a white police officer has set off weeks of largely peaceful protests and led to the dismissal of the city's police chief.